Decoding an Abnormal ECG: Right Bundle Branch Block (RBBB)

Every heartbeat is controlled by an electrical signal. An electrocardiogram — ECG or EKG — can measure these signals. EKGs often pick up electrical signals that look a little different than normal. A right bundle branch block (RBBB) is an example of one of those abnormalities. 

For some people, a RBBB is nothing to worry about and does not mean anything is wrong with their heart. But it can also be a sign of an underlying heart problem. We’ll go through what you need to know if your EKG is abnormal with a RBBB.

What is a right bundle branch block? 

A RBBB is a pattern an EKG can pick up. It happens when the right side of the heart is beating a little bit differently than the left. To understand what this means, let’s take a brief look at how an EKG measures a heartbeat. 

Every heartbeat starts with an electrical signal at the top of the heart. That signal then travels down the heart from top to bottom. As it travels, it tells the heart to beat. An EKG detects these electrical signals and then translates them into the squiggly lines you see on the EKG. A RBBB is a pattern that happens when the electrical signals travel slower down the right side of the heart. 

What does a RBBB look like on an abnormal EKG?

If you have a RBBB, it will cause your EKG to have a specific pattern. Every heartbeat creates a wave on the EKG. With a RBBB, that wave is stretched out and another looks like “bunny ears.” 

What causes a RBBB? 

Several different things can cause a RBBB. In some people, it’s a normal finding. In others, it may be due to an underlying health condition that changes the way the heart beats. The most common conditions that cause a RBBB include:

• COPD (chronic obstructive pulmonary disease): The right side of the heart can get bigger with emphysema and chronic bronchitis. This can change the way the electrical signals move through the heart muscle.

• Pulmonary hypertension: This occurs when there is high blood pressure in the blood vessels of the lungs. When this happens, the heart has to work harder to push blood through the lungs. This has a bigger effect on the right side of the heart. 

• Obstructive sleep apnea (OSA): OSA is a sleep-related breathing condition that causes a person to breathe abnormally while asleep. It can lead to pulmonary hypertension, which can then lead to a RBBB. 

• Pulmonary embolism: This is a blood clot in the lung, which can affect the way blood moves through the lungs. This can also cause changes to the heart similar to pulmonary hypertension. 

• Myocarditis: This is inflammation of the heart tissue or heart valves. And it can cause a RBBB if it affects the right side of the heart. 

• Coronary artery disease (CAD): CAD or a heart attack can lead to a RBBB if they cause permanent damage to the heart muscle.

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In addition to the above conditions, sometimes a person will develop a RBBB for just a short period of time. Reasons for this include:

• Chest trauma: If someone has blunt force to the chest, it can temporarily change the way electrical signals move through the heart. For example, this can happen in a high-speed car crash when an airbag hits someone’s chest.

• Cardiac catheterization: This procedure provides more information about the heart and the blood supply to the heart. It may cause a temporary RBBB. After the procedure is complete, the RBBB usually resolves on its own.

Does a RBBB cause symptoms? 

A RBBB itself does not cause symptoms. But if it’s a sign of an underlying condition, like the ones listed above, that condition can sometimes cause symptoms. So the associated symptoms depend on the underlying condition. 

What should you do if you’ve been diagnosed with a RBBB? 

If you have a RBBB on your EKG, talk to your provider about the next steps. In many cases, you won’t need further evaluation if you’re healthy and don’t have any symptoms. 

But your provider may recommend more tests if:

• You’re having symptoms of one of the above conditions — like new chest pain or shortness of breath.

• You have a known heart or lung condition, and the RBBB is a new change on your EKG.

• You’re at high risk of one of the above conditions.

Some additional tests include:

• Chest X-ray: This can help diagnose lung conditions or changes to the shape of the heart.

• Echocardiogram: This is an ultrasound of the heart that looks at heart function.

• Stress test or cardiac catheterization: This can diagnose coronary heart disease.

How serious is a RBBB? 

If a person is otherwise healthy, a RBBB usually doesn’t cause any problems. But if someone has additional heart conditions — like a history of a heart attack — then a RBBB can be more serious. Your provider can work with you to figure out what getting diagnosed with RBBB means for you — and whether or not it is a sign of something more serious.

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Written by:

Cherilyn Davis, MD

Cherilyn Davis, MD, is a board-certified pediatrician in New York City. She has held local and national roles at the American Medical Women’s Association including board member of the physician division and physician chair of social media.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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